This invention relates generally to parts inspection methods and systems and, more particularly, to evaluation of highly polished substrate surfaces.
Many optical devices, such as ring laser gyroscopes, include highly polished components, such as substrates utilized in making mirrors. Operation of such devices is greatly dependent upon the quality of the mirrors. For example, super-polish quality of a substrate surface, that is, a lack of scratches and other inconsistencies in the substrate surface, is one factor that determines the amount of light scattered from a polished substrate which has been coated with a reflective material. Currently, subjective inspection techniques are utilized for inspection of polished substrates and have been found inadequate for measuring super-polished substrate surface quality and maintaining processes for producing super-polished surfaces. In one known inspection process, the resolution of the inspection is limited by an amount of operator training, operator patience, operator eyesight, as well as an optical configuration of the inspection system. As such, consistent inspection quality is difficult to achieve.
In another inspection process, the polished substrate surfaces are coated with a reflective compound and the resultant mirror products are used to evaluate the super-polish quality of the substrate. However, evaluating the super-polish process by using the coated mirror products delays feedback to the substrate polishing process and is also subject to factors external to the polishing process. Further, because the substrates are coated with the reflective compound prior to inspection, substrates with flawed surfaces may be coated which increases manufacturing costs as more costly pieces (i.e. the coated substrates) may have to be scrapped or reworked. With a better substrate inspection process, flaws in highly polished substrate surfaces could be detected, and possibly corrected, before the reflective compound is applied to a flawed polished surface substrate.